State whether the following statement is true or false:
Oxygen is returned to the atmosphere in only one major process,that is,respiration.

$(a)$ What makes the biosphere a stable system?
$(b)$ What happens when the components of the biosphere interact with each other?

What is the difference between nitrification and denitrification?

Mention the three processes in which oxygen is used up from the atmosphere and the only process in which it is returned to the atmosphere.

Simran and Ria were enjoying dancing in the rain. Suddenly, a question struck Ria's mind: "How does rain fall on Earth?" To this, her elder sister Simran explained the water cycle: how clouds are formed when water evaporates due to the heating of water bodies, rises, expands, and cools to form tiny droplets that grow larger to form clouds, which then sprinkle rainwater onto the Earth. Simran also told Ria that this rainwater is essential and precious and must be conserved.
$(a)$ Which values are displayed by Simran?
$(b)$ Why is water conservation necessary?

The process of nitrogen-fixation by bacteria does not take place in the presence of